NEW YORK — As new names emerged Saturday among the victims of arrested New York money manager Bernard Madoff who are waiting to hear how much of their stake is left, it also became clear that warning signs about Madoff's fund had abounded for years.

The roster of potential victims of Madoff, 70, a former Nasdaq stock market chairman, in what prosecutors said was a $50-billion Ponzi scheme has grown exponentially. The list of people who lost money may number in the hundreds or even thousands.

Among institutions that believe they lost millions are the North Shore-Long Island Jewish Health System and the Texas-based Julian J. Levitt Foundation.

The damage appears to be deepest in the small world of Jewish philanthropy, where Madoff was a leading figure.

But hedge funds and other investment groups looked like big losers, too. The Fairfield Greenwich Group said it had about $7.5-billion in investments linked to Madoff. A private Swiss bank, Banque Benedict Hentsch Fairfield Partners SA, said it had $47.5-million worth of client assets at risk.

The town of Fairfield, Conn., said it placed nearly 15 percent of its retiree pension fund with Madoff. Officials were scrambling to determine how much of the $42-million remained.

Outside analysts had raised concerns about Madoff's firm for years. The company made its own trades and held the shares it bought, unusual practices that kept its activities hidden from view.

Madoff also avoided filing disclosures of its holdings with the SEC; the company said that at the end of every reporting period it sold its holdings and held only cash. Such a tactic is highly unusual because it exposes a fund to large losses by forcing it to sell assets without regard to price.

Madoff, though a pioneer of electronic trading, also refused to provide clients online access to their accounts.

"This was extremely secretive, even for the nontransparent world of hedge funds," said Jake Walthour Jr., head of advisory services for Aksia, a New York consulting company that advised clients not to invest.

But many investors, in a bull-market rush to get in on the action, either ignored the red flags or didn't bother to look for them.

The alleged scheme dated to at least 2005, according to authorities, and appears to have unraveled as investors asked for their money back during the bear market that began 14 months ago.